All-electric control of skyrmion-bimeron transition in van der Waals heterostructures

Abstract

Two-dimensional van der Waals materials offer a versatile platform for manipulating atomic-scale topological spin textures. In this study, using first-principles and micromagnetic calculations, we demonstrate a reversible transition between magnetic skyrmions and bimerons in a MoTeI/In_2Se_3 multiferroic heterostructure. The physical origin lies in the reorientation of the easy axis of magnetic anisotropy, triggered by the reversal of ferroelectric polarization. We show that the transition operates effectively under both static and dynamic conditions, exhibiting remarkable stability and flexibility. Notably, this transition can be achieved entirely through electric control, without requiring any external magnetic field. Furthermore, we propose a binary encoding scheme based on the skyrmion-bimeron transition, presenting a promising path toward energy-efficient spintronic applications.

Figures (4)

• Figure 1: Structural and magnetic properties of MoTeI monolayer and MoTeI/In$_2$Se$_3$ heterostructure. Schematic diagram of a skyrmion and b bimeron switching in a 2D vdW magnetic layer (top) controlled by ferroelectric polarization reversal (bottom). c Top and side views of the atomic structure of the MoTeI monolayer. d Two spin configurations with opposite chirality, used to determine the in-plane DMI parameters, with red arrows indicating the spin orientations. e Side view of the MoTeI/In$_2$Se$_3$ heterostructure, depicting the two distinct polarization states, labeled P$\uparrow$ (left panel) and P$\downarrow$ (right panel). Dependence of magnetic anisotropy energy (MAE) on the polar angle $\theta$ in the f P$\uparrow$ and g P$\downarrow$ configurations for the MoTeI/In$_2$Se$_3$ heterostructure, respectively.
• Figure 2: Ferroelectric modulation of MAE in MoTeI/In$_2$Se$_3$ heterostructure. Layer-resolved partial density of states (PDOS) of the MoTeI/In$_2$Se$_3$ heterostructure in the a P$\uparrow$ and b P$\downarrow$ configurations. c Atomic-resolved MAE comparison between the intrinsic MoTeI monolayer and the polarized MoTeI/In$_2$Se$_3$ heterostructure. Orbital-resolved MAE contributions from Te and I atoms in the MoTeI/In$_2$Se$_3$ heterostructure for both d, e P$\uparrow$ and f, g P$\downarrow$ configurations. PDOS of h Te and i I atoms within the MoTeI/In$_2$Se$_3$ heterostructure. The green arrows indicate the spin-down unoccupied states of the $p_x / p_y$ orbitals and the spin-up occupied states of the $p_y / p_x$ orbitals.
• Figure 3: Equilibrium States of Skyrmions and Bimerons.a Spin configurations of equilibrium skyrmions (left column) and bimerons (right column). The yellow dashed lines indicate the direction along the diameter of a skyrmion/bimeron. b The magnetization components $m_x$, $m_y$, and $m_z$ along the diameter direction of equilibrium skyrmions and bimerons. The colored dots represent the simulation results, and the black lines are analytic curves based on Eq.(\ref{['3']}). c Simulated L-TEM images of equilibrium skyrmions and bimerons. Statistics of thirty sets of d energy and e topological charge data for skyrmion/bimeron relaxed from random magnetization. The dashed lines represent the average values. f Comparison of the average exchange energy $E_{\rm exch}$, anisotropy energy $E_{\rm anis}$, and demagnetization energy $E_{\rm demag}$ for equilibrium skyrmions and bimerons. g The average effective field vectors $\textbf{B}_{\rm eff}$ and anisotropy field vectors $\textbf{B}_{\rm anis}$ for equilibrium skyrmions and bimerons.
• Figure 4: Dynamic skyrmion-bimeron transition and its application as an encoder.a Dynamic snapshots of the moving skyrmion/bimeron in a nanotrack, taken at 0.2 ns, 1.0 ns, and 2.0 ns. b Dynamic snapshots of local spin configuration at the moment of skyrmion-bimeron transitions, taken at 0.51–0.55 ns and 1.56–1.60 ns. Time-dependent variations in c position $(x,y)$ and d velocity $(v_x,v_y)$ during the skyrmion/bimeron motion. The colored dots represent the simulation results, and the black lines are analytic curves based on Eq.(\ref{['5']}). The green dashed lines mark the moment when the skyrmion-bimeron transitions occur. Time-dependent variations in e electric field $E_{\rm c}$, f total energy $E$, and g topological charge $Q$ during the skyrmion/bimeron motion. A scheme for a dynamic skyrmion-bimeron encoder, with h the electric field as the input signal and i the total energy as the output signal. The output signal is controlled to represent the binary ASCII code of "SKYRMION."